1. Field of the Invention
The present invention relates to an optical pickup that records and/or reproduces information signals on and/or from an optical disc, and an optical disc apparatus using the optical pickup.
2. Description of the Related Art
Hitherto, an optical disc, such as a compact disc (CD) or a digital versatile disc (DVD); or to achieve further high-density recording, an optical disc for recording/reproducing signals using an optical beam with a wavelength of about 405 nm emitted from, for example, a blue-violet semiconductor laser, this type of optical disc being hereinafter referred to as “high-density recording optical disc”, has been used as a recording medium for information signals. An optical disc apparatus has been used for recording information signals on such an optical disc, or reproducing information signals recorded on such an optical disc.
Such an optical pickup is being desired to be compatible with a plurality of types of optical discs. Hence, to be compatible with optical discs in different formats with different usable wavelengths and different thicknesses of protection substrates, an optical pickup is being provided, which uses a plurality of optical beams with different wavelengths and has a plurality of objective lenses (for example, see Japanese Unexamined Patent Application Publication No. 2006-4547).
The optical pickup having the plurality of objective lenses includes an objective lens drive unit having a fixed portion and a movable portion. For example, two objective lenses are aligned in a tangential direction or a radial direction on a lens holder functioning as the movable portion of the objective lens drive unit. The optical pickup selects one of the objective lenses depending on the format and type of an optical disc.
The optical pickup also includes optical systems for respectively guiding optical beams with wavelengths corresponding to the objective lenses. In general, an optical beam guided in a plane orthogonal to an optical axis of an objective lens is reflected and raised with a raising mirror toward the objective lens, thereby collecting the optical beam onto the optical disc with the objective lens.
Meanwhile, such an optical pickup is demanded to reduce a distance between the objective lenses for reduction in size and weight of the movable portion as well as the entire optical pickup. To reduce the distance between the objective lenses, it is necessary to reduce a distance between the raising mirrors corresponding to the objective lenses. For example, if two objective lenses and two raising mirrors are provided and optical paths to the raising mirrors do not define an angle to each other within a plane, that is, if optical beams are incident on the raising mirrors in the same direction, or opposite directions, the sizes of the raising mirrors are reduced to a limit of an effective area corresponding to apertures of the objective lenses. In addition, the raising mirrors are adjacently arranged, thereby reducing the distance between the raising mirrors, and the distance between the objective lenses.
However, in view of the optical systems, and reduction in size of the entire optical pickup, an optical path of an optical beam being incident on one of the raising mirrors may define an angle to an optical path of an optical beam incident on the other of the raising mirrors. In such a case, the distance between the raising mirrors may be increased by thicknesses of the raising mirrors. Owing to this, the distance between the objective lenses may be increased, and the size of the lens holder functioning as the movable portion may be increased.